It is generally known in the art to syphon or “bleed” air from a compressor section of a turbine engine upstream from the combustion section. Such bleed air is used for a variety of functions including but not limited to cabin pressurization, engine operability, powering of pneumatic actuators, anti-icing, etc.
Many contemporary systems modulate such bleed air through the use of multiple air valves. Each air valve is in fluid communication with a certain portion of the compressor section. Controlling the restriction offered by the internal metering element of each air valve controls the amount of bleed air that is allowed to flow from the compressor section. This modulated bleed air flows from each air valve to its appropriate destination to achieve one or more of the exemplary functions identified above.
Unfortunately, such contemporary systems are complex. Indeed, they typically involve multiple stand-alone air valves each having an independent actuator, or at least multiple separate metering elements controlled by a single actuator, each being connected to the single actuator by way of a relatively complex linkage. As one example, a stage of compressor section may utilize two stand-alone air valves each having an actuator, or a single valve having two metering elements therein which are connected by way of a linkage to a single actuator. While the above systems have proven to sufficiently modulate bleed air, they also have a large overall engine foot print, have a large part count, are generally complex in their linkages, and tend to be high cost.
Recent designs have included a single metering element that allows for a primary bleed air function as well as a secondary function. While such systems present a significant improvement over existing designs, the applicant has found that for smaller bleed valve port sizes, on the order of about two inch port diameter, (i.e. smaller bleed functions) such designs are not as efficient in terms of space and weight. That is, despite this smaller bleed function, such systems require a sufficiently large actuator to deal with internal resistive torque on the metering element. For smaller bleed functions, there is an expectation of smaller size and weight envelope as well, however. As such, there is a need in the art for an apparatus and method that modulates bleed air in smaller bleed applications that presents a reduced amount of internal frictional forces and resistive torque so as to reduce overall actuator size requirements.
The invention provides such an apparatus and method. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.